Gel electrophoresis is a widely used and highly effective technique for separating complex mixtures of chemical species. While the gels used in different types of electrophoresis apparatus may vary in shape, a common gel configuration is that of a thin flat slab. Gel slabs offer many advantages, including ease of evaluation by quantitative densitometry and photographic techniques, ease of drying and printing by autoradiography and other contact print methods, a geometry which permits improved heat dissipation and thus the opportunity for high voltage gradients, and the ability to perform simultaneous separations on a number of samples, for comparison as well as efficiency.
In many applications, the slab is most conveniently cast in a sandwich-type arrangement between two flat glass plates, and then used in an electrophoresis procedure while still held between the plates. Clear glass plates permit monitoring of the gel-forming solution as it is injected into the space between the plates, as well as monitoring of the finished slab and other adjacent portions of the entire apparatus while electrophoresis is taking place. The separation between the plates is typically maintained by spacer strips along the opposing vertical side edges. The entire assembly is held together by a clamp at each vertical edge. While the pressure exerted by the clamps must be tight enough to ensure a seal, it is frequently difficult to provide a pressure which is sufficiently even and controllable to reduce the danger of breakage of the glass.